The Fibre Channel (“FC”) is an architecture and a hierarchical set of protocols that define a data communications network for interconnecting a number of different computers and peripheral devices. The FC supports a variety of upper-level protocols, including the Small Computer Systems Interface (“SCSI”) protocol. A computer or peripheral device is linked to the network through an FC port and copper wires or optical fibres. An FC port includes a transceiver and an interface controller. The computer peripheral device in which an FC port is contained is called a “host,” and the combination of an FC port and a host is called an “FC node.” An FC port exchanges data with a host via a local data bus, such as a Peripheral Computer Interface (“PCI”) bus. The interface controller controls lower-level protocol exchanges between the fibre channel and the computer or peripheral device in which the FC port resides.
An interface controller within an FC port serves essentially as a transducer between serial receiver and transmitter components of the FC port and the host processor of the FC node in which the FC port is contained. On the input side, the interface controller is concerned with assembling serially-encoded data received from the receiver component into ordered sets of bytes, assembling the ordered sets of bytes into FC primitives and FC frames, performing internal state transitions in order to conform to lower-level FC protocols, and passing FC frames, along with status information, to the host processor within the context of larger collections of FC frames, called FC sequences and FC exchanges. On the output side, the interface controller accepts host memory buffer references and control information from the host processor and transforms them into FC frames within the context of FC sequences and FC exchanges, providing the FC frames to the transmitter component of the FC port for serial transmission to the FC, and transmits FC primitives in response to received FC primitives and state transitions in order to conform to lower-level FC protocols.
FC nodes may transmit and receive data through the FC at different rates. It is desirable for FC nodes, upon power up and initialization, to automatically determine the highest common data transmission and reception rate among all the nodes of the FC network in order to maximize data transmission rates through the FC. According to Fibre Channel Framing and Signaling (FC-FS) standards, each FC port is allowed to support up to four different speed rates. The problem with two FC interfaces communicating over a DWDM transport network is that either each edge device needs to be preconfigured to the same single rate or the complex FC speed negotiation state machine needs to be implemented at both edges. The acronym DWDM refers to Dense Wavelength Division Multiplexing, which is an optical technology used to increase bandwidth over existing fiber optic backbones by combining and transmitting multiple signals simultaneously at different wavelengths on the same fiber.
Therefore, a need exists for a method avoiding complex speed negotiation state machines as per FC-FS standard to make the DWDM transport behave like a virtual wire with respect to the FC ports and allow the FC clients to negotiate the desired speed directly between themselves. A primary purpose of the present invention is to solve these needs and provide further related advantages.